Fixed restorative treatments are commonly used to arrest a deteriorating dental condition. In fact, increased lifestyle demands of the aging general population has resulted in an increasing number of patients seeking fixed restorative treatment for the undermined cosmetics and function that frequently accompany a deteriorating dental condition. One such treatment sought is a dental implant supported prosthesis.
Dental implants are well known in the art and restorative techniques currently used for pre-fabricated devices were developed many years ago, between 1930 and 1950. The restorative techniques used for implant supported restorations are not fundamentally different from the techniques used for the restoration of natural tooth abutments. Briefly, the present customary practice for making a metal framework for an implant supported prosthesis involves making a stone model from the patients mouth, including the simulation of the implants by use of analogues and placing metal cylinders on these analogues. A wax model is then made integrating the metal cylinders and this wax model is lifted off from the stone model and invested and cast. Accordingly, the cylinders are an integrated part of the framework. The framework is completed with gingival tissue simulating material and artificial teeth and the framework is securely seated in the patients mouth by the cylinders being placed over and securely attached to the dental implant abutments. The implant abutments are previously implanted into the patients mouth
The dental implant abutment, however, raises several concerns, many of which are not material in natural tooth abutments. Implant abutments obviously lack the periodontal ligament complex located around natural teeth. The absence of periodontal ligaments precludes the implant abutment from moving within the stomatognathic system to the same degree as natural abutment teeth. Existing implant abutments, as described briefly above, may introduce unacceptably high stresses into the bone-implant-abutment complex because of undetected frame-to-implant fit discrepancies. This stress may result in the loosening of fixation screws, stress induced resorption of bone and, ultimately, failure of the implant.
Because existing restorative techniques and systems use impression or model and die systems, inconsistent volumetric and linear expansion are frequently manifested during seating of the framework. This expansion results in the creation of unacceptably high tension on abutment teeth and implant abutment components. Vertical dimensional changes are also not uncommon in existing implant restorations and often result in insufficient abutment to restoration contact area.
Additionally, standard laboratory techniques of casting the implant framework from a stone model of the mouth do not permit the high volume fabrication of single-unit cast frameworks to a high degree of accuracy. This is because the tolerances between the second generation cast based on the stone model and the actual measurable fit dimensions of the mouth are unacceptably high. Thus, in multiple abutment situations the high volume castings of existing restoration systems often require dividing them into several segments in order to achieve an acceptable fit. These segments are then soldered together before placement in the mouth and attachment to the implant abutment. This segment casting method necessitates labor intensive and technique sensitive soldering operations. Accuracy levels vary dramatically after soldering the segment castings together and subsequently substantial time is required to finalize the implant restoration fit.